NEW-AGE CONTROL ON THE PORT HURON MORAINE IN NORTHERN MICHIGAN

Until now, radiocarbon age estimates of the Port Huron moraine in Michigan have been based largely on C-14 dates from beyond the state. This study reports a radiocarbon age of 12,960 +/- 350 yr B.P. from sediments immediately proximal to the northwestern part of the Inner Port Huron moraine in Michigan's Southern Peninsula. Geologic relationships indicate that this section of the moraine predates the age estimate. Stratigraphic and morphologic relationships of sediments of ancestral Great Lakes phases related to the Port Huron morainic system, C-14 ages from sediments of those lake phases, and a C-14 age from wood buried by till of the Wyoming moraine (a morphostratigraphic equivalent of the Port Huron moraine), have collectively supported the interpretation that the morainic system was formed between 13,500 and 12,700 yr B.P. Our radiocarbon age estimate, the first from sediments immediately proximal to the Port Huron system in Michigan, is compatible with this interpretation. Furthermore, because the Port Huron moraine in southeast Michigan is interpreted to be equivalent to Ontario's 13,000 year-old Wyoming moraine, the bracketing of the system's northwest section indicates that, within radiometric-dating limitations, these three parts of the massive, extensive, and chronologically important Port Huron morainic system are approximately the same age.